Had a family of beavers move into a small lake-10 acres+\-. They stopped up the flow-through drain pipe and have the lake level up about 5-6 ft forcing flooding through the emergency spillway. We have trapped\killed 5 but still have residents. We will eventually get the remaining I am confident. 

Problem is now how to open the through-the-levy drain pipe. 

Anyone had luck with disrupting a beaver plug in 5-6 ft of water? 

I don't really want to blow a perfectly good levy.

Thanks 

Edit: pipe is 14" and over 60' long. Problem with back hoe at this time is you cant see the water side of the pipe. After corn is planted I hope to take enough 2" plastic pipe  and push it up from dry side to break the seal. If I can even get bubbles to rise, we could locate the inlet to the pipe. Hopefully we might even use the bobcat to push on the 2" pipe to force it through. I'll report on outcome. 

Any other suggestions?